Working with nested containers like pair<int, pair<int, int>> often leads to cluttered code with verbose access patterns such as .second.first. Alternatively, using tuple<int, int, int> introduces its own confusion with syntax like get<2>(x) where indices start from zero. A dedicated triplet template class provides a clean, intuitive solution that eliminates these pain points.

This implementation follows the same design philosophy as C++ standard library's pair, extending it with a third element while maintaining familiar usage patterns.

---

Obtaining the Code

The implementation is available on GitHub at https://github.com/Jerrycyx/triplet. Download the latest release from the releases page.

Integration Method 1: Header-Only

Place triplet.h in your project directory and include it with #include "triplet.h" (note the quotation marks required for local headers). Alterntaive locations are supported using relative or absolute paths.

Integration Method 2: Embedded in Single Files

For competitive programming contexts requiring a single submission file, you can copy the contents of triplet.min.h (excluding the header guard macros at the beginning and end) directly into your source code.

---

Usage Guide

The triplet template mirrors std::pair's interface, so users already familiar with standard containers will find the transition seamless.

Summary: The interface adds a .third member while construction, initialization, and comparison behave identical to pair.

Construction and Initialization

triplet<int, int, int> container;                    // Default construction
triplet<int, int, int> container(10, 20, 30);        // Constructor initialization
triplet<int, int, int> container = {10, 20, 30};     // Brace initialization

Uninitialized triplets invoke the default constructor of their element types. For convenience, a factory function mirrors make_pair:

auto result = make_triplet(5, 15, 25);  // Returns triplet<int, int, int>{5, 15, 25}

Accessing Elements

• First element: container.first
• Second element: container.second
• Third element: container.third

The naming convention follows pair's established pattern, making it intuitive and memorable.

Comparison Operators

Six comparison operators are overloaded: ==, !=, <, >, <=, >=. The comparison semantics follow lexicographic ordering:

• Equality (==): All three elements compare equal
• Inequality (!=): At least one element differs
• Less than (<): Compares first first, then second, then third as tiebreakers
• Greater than (>): Inverse of less then
• Less than or equal (<=): Equivalent to !(x > y)
• Greater than or equal (>=): Equivalent to !(x < y)

These operators require only that element types support < and == operations with a valid partial ordering (meaning x < y and y < x cannot both be true for any values).

---

License

This implementation is distributed under the Mozilla Public License 2.0 (MPL-2.0).

Key obligations include preserving original copyright notices, license headers, and disclaimers in all distributions. Modified versions distributed in source form must include appropriate notices and comply with MPL-2.0 terms. Original license declarations must not be removed or altered.